This invention relates to high molecular weight phenolphthalein-dihydroxy aromatic compound polycarbonates having a mole ratio of phenolphthalein to dihydroxy aromatic compound in the range from about 0.05 to 0.7.
Polycarbonate resins made from 4,4'-isopropylidenediphenol (bisphenol A) have been known to the plastics art for some time and are characterized as having exceptionally high impact strength. Although this property and other desirable properties for such conventional polycarbonates make them useful for certain applications, the polymers' relatively low resistance to the effects of heat, stress and organic solvents prevents their use in many other applications. These properties and limitations are described in detail in the book, "Chemistry and Physics of Polycarbonates", written by H. Schnell and published by Interscience Publishers (1964).
Improved polycarbonate resins made from phenolphthalein are described in U.S. Pat. No. 3,036,036 (1962) and an article written by P. W. Morgan (Journal of Polymer Science: Part A, Vol. 2, page 437, (1964)). These resins have higher melting points, higher heat distortion temperatures and better solvent resistance to chlorinated alkane solvents than resins made from 4,4'-isopropylidenediphenol. Copolycarbonates of phenolphthalein and 4,4'-isopropylidenediphenol were also described. However, the molecular weights of these copolycarbonates were so low that only fibers or films were produced from them and molded articles made from such products have been found to have virtually no impact strength.
Copolycarbonates of phenolphthalein and 4,4'-isopropylidenediphenol are also disclosed by Smirnova, et al. Polymer Science U.S.S.R. A10, pages 118-124 (1968). However, these copolycarbonates are of such a high molecular weight that they are impractical to use as molding resins since they are virtually impossible to injection mold.